Motor drive device and drive method

Abstract

A reverse current detection unit detects the direction of the motor current during the synchronous rectifier period based on the polarity of the on voltage of a switching device contained in the motor current path, and outputs a reverse current detection signal representing the result of this detection to the PWM control unit. Change in the output of the PWM control unit that generates the drive signal for a particular switching device in the drive unit is controlled based on the reverse current detection signal and the energizing pattern of the drive unit is changed when motor current is detected in the synchronous rectifier period to be flowing in the opposite direction as in the urging period. The flow of motor current to the power supply is thus reduced and a rise in the power supply voltage can be prevented.

1. A motor drive device operable to supply drive power to a motor by switching repeatedly between an urging state and a regeneration state, comprising:
 a drive signal generator operable to generate a drive signal; 
 a driver having high potential side switching devices for N phases (where N is an integer greater than or equal to 2) and low potential side switching devices for N phases, said driver being operable to produce the drive power as a result that the high potential side switching devices for N phases and the low potential side switching devices for N phases are controlled by the drive signal; 
 a reverse current detector connected in parallel to either the high potential side switching devices for N phases or the low potential side switching devices for N phases, said reverse current detector being operable to detect, based on the polarity of the on voltage of said switching devices connected to said reverse current detector, a time when the direction of motor current flowing through the motor reverses in the regeneration state and to generate a reverse current detection signal; 
 a current detection unit operable to detect the motor current level of the motor and to output a current detection signal; and 
 a torque control signal generator operable to generate a torque control signal setting the motor torque; 
 wherein said drive signal generator controls the logic level of the drive signal based on this reverse current detection signal; and 
 said drive signal generator controls the logic level of the drive signal based on the difference between the current detection signal and the torque control signal. 
 
     
     
       2. The motor drive device described in  claim 1 , wherein:
 said drive signal generator produces N-phase high potential side drive signals operable to control the N-phase high potential side switching devices, respectively, and N-phase low potential side drive signals operable to control the N-phase low potential side switching devices, respectively; and 
 in the urging state for any single phase, the high potential side drive signal is set to an operating state level and the low potential side drive signal is set to a non-operating state level, or the high potential side drive signal is set to a non-operating state level and the low potential side drive signal is set to an operating state level. 
 
     
     
       3. The motor drive device described in  claim 2 , wherein said drive signal generator controls the logic level of the high potential side drive signal and low potential side drive signal for at least one phase to the logic level of the urging state when the reverse current detection signal is output. 
     
     
       4. The motor drive device described in  claim 2 , wherein said drive signal generator controls the logic level of both the high potential side drive signal and low potential side drive signal for at least one phase to the non-operating state level when the reverse current detection signal is output. 
     
     
       5. The motor drive device described in  claim 2 , wherein said drive signal generator holds the logic level of the high potential side drive signal and low potential side drive signal for at least one phase to the logic level of the state just before the reverse current detection signal was output for a first predetermined time when the reverse current detection signal is output. 
     
     
       6. The motor drive device described in  claim 2 , wherein said drive signal generator controls the logic level of either the high potential side drive signal or low potential side drive signal for at least one phase to the non-operating state level for a second predetermined time when the reverse current detection signal is output. 
     
     
       7. The motor drive device described in  claim 2 , wherein said driver outputs the on voltage of the switching device for at least one phase selected from a group of N-phase high potential side switching devices or a group of N-phase low potential side switching devices; and said reverse current detector generates the reverse current detection signal based on a comparison of the on voltage and a predetermined voltage. 
     
     
       8. The motor drive device described in  claim 7 , wherein said driver comprises a separate switching device parallel connected to the switching device for at least one phase in at least one group of switching devices, and sets the separate switching device to the non-operating state in the regeneration state.